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Re: does facealpha work?


From: Ben Abbott
Subject: Re: does facealpha work?
Date: Fri, 25 Jul 2014 12:15:42 -0400

On Jul 25, 2014, at 10:30 AM, Francesco Potortì <address@hidden> wrote:

>> I have tried fill() and 'FaceAlpha" property, but cannot obtain the
>> results I want.  By changing facelpha i can change the colour, which
>> becomes paler, but not transparent, as the filled areas below cannot be
>> seen.  I use the gnuplot backend.
>> 
>> Is there anything obvious that I should know?  Do I need to provide an
>> example or is this a known problem?
> 
> Here is an example:
> 
> hold on
> p1 = patch([0 0 2], [0 2 1], "r")
> p2 = patch([2 2 0], [0 2 1], "g")
> hold off
> 
> This draws two partially overlapping triangles of different colours, as
> expected.  Now I set the facealpha property on both to make them
> partially transparent:
> 
> set (p1, "facealpha", 0.2)
> set (p2, "facealpha", 0.2);
> 
> Both colours become less saturated, but they remain opaque.  Is this a
> bug?

I don't think is facealpha is supported by Octave for the gnuplot toolkit. If 
my recollection is correct, the problem is that Gnuplot doesn't support 
transparency for postscript output, and Octave derives nearly all output from 
an eps-file.

Ben




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